This invention concerns improvements in pumping apparatus, and more especially, but not exclusively, to apparatus for use in the pumping of fluid materials containing entrained gas pockets. Such materials may include, for example, gaseous sludges and/or like materials which give off gases when circulated in a centrifugal pump, and also liquids which contain entrained air owing, for example, to admission of air into an intake pipe of a centrifugal pump owing to exposure of the inlet to the pipe.
It is known that a centrifugal impeller pump may become gas-locked owing to an accumulation of gas pockets around blades of the pump impeller, due either to inherent gas within the material being pumped being given up as a result of agitation of the material within the pump, or, owing to inadvertent leakage of air into the intake of the pump.